Losing Albedo

The Earth's albedo is declining, why does that matter?

You might occasionally see a news story about albedo and dismiss it as a technical concept not worth your time. After all, what is "albedo" anyway?!

Albedo may be an extraordinarily complex topic but it's also something that's very easy to understand. Try standing in the full sun while wearing a black shirt and pay attention to how quickly you heat up, then try it again while wearing a white shirt and notice the difference.

The difference you notice is due to the fact that white surfaces reflect sunlight and stay cooler, while dark surfaces absorb sunlight and heat up. The degree of reflected light is called albedo, and it's measured from "0" for black surfaces that absorb all light, to "1" for white surfaces that reflect all light.

This is an intriguing concept, and you may pay more attention to albedo than you realize. For example, it might factor into what clothes you wear on a given day, what color of car you decide to buy, or where you stand in the sunshine. However, albedo also happens on a global scale, and this is why you see it in the news.

On a global scale the Earth both absorbs sunlight and reflects sunlight back into space. When these factors are in balance the Earth maintains a consistent temperature, but if these factors fall out of balance the Earth begins to either heat up or cool down and that's what's happening now.

Not only have we fallen out of balance but humans have triggered a number of devastating feedback loops. For example, when highly reflective snow and sea ice begins to melt then albedo levels decline (i.e. we lose albedo) as the Earth absorbs more of the sun's heat instead of reflecting it. Then as the Earth heats up, even more snow and sea ice melts, revealing more dark surfaces and making things even hotter, creating a cycle that's almost impossible to break out of.

We read about melting snow and sea ice all the time, but scientists were puzzled because this didn't fully account for the larger decline they were seeing in the Earth's albedo. However, more recent research has found an overlooked feedback loop that might be the missing piece.

While cool, moist conditions in the lower atmosophere promote the formation of low-level clouds, global warming means these clouds are now thinning or dissipating, letting more sunlight reach the Earth's surface. This sets up a feedback loop where low-level clouds are disappearing due to warming, and missing clouds lead to even more warming.

It's fascinating that a process we sense directly on our skin is also felt on the "skin" of the planet. In other words, we can literally stand in the sun and feel what the Earth is feeling.

It's a realization that breathes life into an important story—a story we might otherwise gloss over.